Several patents are directed to water soluble polyamides. U.S. Pat. No. 3,882,090 to Fagerberg et al., issued May 6, 1975 relates to linear water-soluble polyamides having ether linkages in the polymer chain. The polyamides are useful as textile sizing agents, coatings, adhesives and water soluble films.
U.S. Pat. No. 5,053,484 to Speranza et al., issued Oct. 1, 1991 relates to polyether amides produced by reacting a polyethylene glycol diamine and a first dicarboxylic acid or an ester thereof, with a polyoxyalkylene diamine of a molecular weight of at least 500 and a second dicarboxylic acid or an ester thereof.
U.S. Pat. No. 5,118,785 to Speranza et al., issued Jun. 2, 1992 relates to polyether amides produced by reacting aromatic dicarboxylic acids with tetraethylene glycol diamine. The resulting polyether amides are useful to make polymers and fiber, with unusually good water absorbency properties.
U.S. Pat. No. 5,086,162 to Speranza et al., issued Jun. 28, 1994 relates to polyether amides produced by reacting at least one polyoxyalkylene glycol diamine with at least two different carboxylic acid or esters thereof The polyamides exhibit improved water absorbency, and/or solubility in water.
U.S. Pat. No. 5,324,812 to Speranza et al., issued Jun. 28, 1994 relates to water soluble polyamides produced by reacting two different carboxylic acids with at least one low molecular weight poly(alkylene glycol) diamine and at least one relatively high molecular weight polyoxyalkylene diamine. Such water soluble polyamides are taught to be useful in hot melt adhesive formulations.
Collectively, the polyamides taught in Speranza either exhibit a high melt point, or in the case of those polyamides having lower melt points, are disadvantageous in that the polyamides tend to block once formed into an adhesive.
WO 96/08538, published Mar. 21, 1996 is directed to a remoistenable adhesive wherein the remoistenable adhesive is a hot melt consisting of a water soluble polyamide. The water soluble polyamide may be optionally combined with a tackifier or wax.
Although water soluble polyamides have been identified for use as remoistenable adhesives, such class of polymers tend to disadvantageously have a high melt point, relatively high molten viscosity and slow speed of remoistening. Attempts to reduce the melt point and viscosity by means of formulating the polyamides with conventional hot melt adhesive additives such as tackifiers and waxes often results in diminished blocking resistance. Hence, industry would find advantage in water sensitive adhesive compositions having a low viscosity, fast rate of remoistening, that also possess the desired blocking resistance.